This invention relates to a shock absorber or oscillation damper and moreover particularly to a shock absorber to be used as or as a part of a suspension strut in a vehicle. A suspension strut is to be understood as a component of a vehicle which, besides a shock absorbing function, has also a wheel guiding function and is therefore subject to transverse forces and to bending moments. For more detailed information on suspension struts it is referred to a brochure SACHS Function and Workshop Hints for Vehicle Parts No. 850506, edition 1985, and more particularly to pages 6 and 7 of this brochure.
It is usual with shock absorbers to provide a guiding sleeve for the piston rod such that a sliding friction occurs on axial movement of the piston rod. In case of suspension struts as defined above, the friction occurring between the piston rod and the sliding sleeve is considerable as a result of the transverse forces and bending moments. This friction forces reduce the driving comfort of the vehicle and result in high wear of the guiding sleeve. This wear of the guiding sleeve may result in undesirable reduction of the damping forces. Moreover, in response to strong transverse forces, a bending of the piston rod may occur, and as a result of such bending the piston rod may be clamped within the guiding sleeve such that the oscillation damper becomes effective only at relatively large axial forces.